I also have a 2010 Silverado LT Crewcab 5.3l engine with the tow group and was wondering when you go over mountains and the truck downshifts, what RPM are you taching? I just went from Virgina to West TN and going over black mountain on the down hill side the grade is 5% for about 6 or so miles and I found that every time I tapped my brakes the truck downshifted and I was taching between 4.5 and 5k RPM. To be honest I do not like this as it does slow you down, but when the speed limit is 65-70 and you have idiots that want to ride their brakes and truckers that want to ride a little close, this rapid decrease in speed I can see causing and issue. But beside that the RPM's has me concerned. Most V8 engines that I'm familiar with red line at 4k or 5k. My truck does not have any yellow or red line marked on the tachometer, but that high of RPM on a V8 can not be good. Do you know what the red line of this truck is?

What axle ratio & tranny does your truck have? Two examples:

6 speed trans'

4.10:1 axle when in 5th (0.85:1) = 3.48:1 final drive ratio

4.10:1 axle when in 4th (1.15:1) = 4.71:1 final drive ratio

3.73:1 axle when in 5th (0.85:1) = 3.17:1 final drive ratio

3.73:1 axle when in 4th (1.15:1) = 4.28:1 final drive ratio

W/ the ratios being what they are in the 6 speed, it's quite a drop going into 4th. That's probably what is causing what you're encountering and rightfully so. A greater than expected deceleration. My truck was ordered w/ the 4.10s (I'm a firm proponent of More's Law ). I was doing the math around the time it was being built (too late to change order) & realized what the final drive ratios were going to be. For whatever reason (whether a mistake or content change), my truck was built w/ the 3.73s. It turns out I'll probably be happier w/ the 3.73s.

Quote:

Originally Posted by slpybeartx

Thanks for those codes, revrnd! I am very intrigued by the "6L80". I would like to trade in my 2008 Z71 for a 2010 Z71 to pick up the new tranny and increased towing power.

I have the Allison transmission option with my Duramax (it is ONLY available on the diesel). I LOVE IT.

Although a very expensive option when I ordered the truck (my dealer had NEVER ordered it "for the lot" before because of that), the trans shifts flawlessly and has an external filter that can be changed easily (even after every long trip if you want to since its a spin on). Tow/Haul mode uses all six gears (just changes the shift profile for when the shift occurs) and up/down shifts automatically for best uphill and downhill speed control. The top two gears are OVERDRIVE gears and we get pretty good fuel mileage hitched or not (though do NOT buy it for fuel economy as it is not much better than the stock 6 speed auto trans and the break even would be several lifetimes).

I also have a 2010 Silverado LT Crewcab 5.3l engine with the tow group and was wondering when you go over mountains and the truck downshifts, what RPM are you taching? I just went from Virgina to West TN and going over black mountain on the down hill side the grade is 5% for about 6 or so miles and I found that every time I tapped my brakes the truck downshifted and I was taching between 4.5 and 5k RPM. To be honest I do not like this as it does slow you down, but when the speed limit is 65-70 and you have idiots that want to ride their brakes and truckers that want to ride a little close, this rapid decrease in speed I can see causing and issue. But beside that the RPM's has me concerned. Most V8 engines that I'm familiar with red line at 4k or 5k. My truck does not have any yellow or red line marked on the tachometer, but that high of RPM on a V8 can not be good. Do you know what the red line of this truck is?
On a slightly different note:
I'm also towing a little popup that has a dry weight of about 1200lbs. Your trailer has a dry weight of about 2600lbs. The truck can tow about 10k. From reading your post I'm seeing you are not having any issues towing that size trailer, but towing my little popup I'm finding it searching for gears when going up any size hill. I would love to buy the size trailer you have but I would like to hear from someone who has one and tows their experience?

Lastly this truck has a trailer brake controller, but for the life of me I can not tell how much stopping power I'm putting on to the trailer. Have you found a way to tell or is the amount done automatically?

I kind of like the feature you're talking about. I tow up and down Black Mountain a few times a year - but only once since I got the new truck - and I'm pretty sure the speed limit is 55 until you get to the bottom. Sorry, I didn't notice the RPMs but I'll look next time. But if you're unhappy with the gear it selects for you, why not put it in manual and select the gear that feels right? That feature works very nicely on the 2010 LT.

I think I tow at about 4,000 pounds. The gross weight for the trailer is around 5,000. As for the brake controller, I use the Prodigy and set it at 6.5. Just had my trailer brakes checked after a year, and they said it was wearing normaly, so I must be estimating it about right. The service guys that installed the controller for me suggested I find an empty stretch of road and adjust the controller while braking, with the goal to make it feel as if the whole rig is braking as a unit.

Going up Black Mountain, my six-speed transmission pulled it like a charm, no hunting. Much, much better than pulling the same trailer with the 2005 with the four-speed and 4.8 liter.

__________________2018 Coachmen Apex 249 RBS
2010 Silverado LT 5.3 V8

The world is a great book, of which those who never stir from home
read only a page. - St. Augustine

The 6L80 is used in 1500 series pickups & the 6L90 in 2500HD & 3500HDs. There are built @ the GM Powertrain plant in Ypsilanti MI.

The Allison 1000 series tranny is the model used w/ the Duramax. It's built in Baltimore MD.

My neighbor just down the street from me works at the Allison plant on Pulaski Highway (Rt40), in Baltimore, the last time I had talked to him he said that his job in Baltimore may be over soon the company was going to move the plant to Mexico I had heard about this in the beginning of the Summer but at this time I don't know what is happening with his job.

One thing I don't like about the 1/2 ton or the heavy duty 1/2 ton is the receiver, a class III is standard, when I put my hitch into the receiver there is too much play and GM will not supply a class IV for any 1/2 ton, the class IV is standard on the 3/4 ton only, with a class IV the hitch fits snug as it did on my 3/4 ton GMC Suburban, and from what I understand one can not get an after market class IV receiver for a GM 1/2 ton pick-up at least not for my 2008.